Air Pollution Hikes Stroke Risk

by: Rita Jenkins

The type of stroke that results when a blood clot travels to the brain — called an ischemic stroke — is more likely to occur on days when the air contains a larger concentration of particulate matter, according to a study published online in Stroke: Journal of the American Heart Association.

Researchers at Beth Israel Deaconess Medical Center (BIDMC) and the Harvard School of Public Health (HSPH) examined air quality on a total of 37,000 days in nine cities. Risk of hospitalization for ischemic stroke was 1 percent higher on days with relatively high levels of air pollution, compared with low-air pollution days, reports lead author Gregory Wellenius, ScD, postdoctoral fellow in cardiology at BIDMC.

Third Cause of Death in US

“Although these effects sound relatively small,” says Wellenius, “given the large number of people exposed to air pollution and the large number of people at risk for stroke … the actual number of strokes could be significant.”

Stroke is the third leading cause of death in the US, affecting more than 700,000 individuals each year.

A “consistent increased risk” for cardiac health problems associated with exposure to ambient air particles was established in earlier research by Wellenius and coauthors Murray Mittleman, MD, DrPH, of BIDMC’s Cardiovascular Epidemiology Research Unit and Joel Schwartz, PhD, of HSPH.

“Air pollution has been shown to trigger heart attacks and to aggravate the conditions of patients with congestive heart failure,” says Mittleman, who is also an associate professor of medicine at Harvard Medical School.

“These new findings, demonstrating that incidence of clot-based strokes also increase, [are] in keeping with our earlier data showing a relationship between air pollution and heart and lung disorders,” he notes.

The researchers also looked at the incidence of hemorrhagic stroke, which is caused by bleeding in the brain, during the same “high pollution” days, notes Wellenius, but found no association between the two.

Reducing Exposure May Lower Risk

The air pollution in question — particulate matter smaller than 10 micrometers in diameter — includes particles from car and truck exhaust, power plants and refineries. The measurements were provided by the US Environmental Protection Agency from nine US cities: Birmingham, Ala., Chicago, New Haven, Conn., Cleveland, Detroit, Minneapolis, Pittsburgh, Salt Lake City and Seattle.

The authors analyzed hospital admissions among a group of Medicare patients with an average age of 79. Seventy-five percent of the patients were white, and 61 percent were female. Their findings showed that during the course of their study, there were 155,503 hospital admissions for ischemic stroke.

The final analysis demonstrated a 1.03 percent rise in ischemic stroke on the days with the highest pollution measures.

“We don’t know exactly what mechanisms are involved that trigger these cardiac events,” says Wellenius. “However, we do know that particulates in the air promote inflammation, which is a significant risk factor for cardiac events; that exposure to particulates can lead to changes in heart rate and blood pressure; and that pollution can cause changes in coaguable states (related to blood clotting abilities).”

The authors say that future research will focus on finding out which pollutants are most toxic, as well as which patients are at greatest risk for health problems stemming from air pollution.

“Taken together with previous work, these latest results support the idea that reducing exposure to particulate matter may reduce the risk of strokes and heart attacks,” they conclude.

Copyright 2005 Daily News Central

About The Author

Rita Jenkins is a health journalist for Daily News Central, an online publication that delivers breaking news and reliable health information to consumers, healthcare providers and industry professionals: www.dailynewscentral.com.

               

Symptoms of Stroke

From the Better Health Channel - Strokes - Signs and Symptoms

Stroke - signs and symptoms

Stroke is often referred to by doctors as a cerebrovascular accident, but the term is not an accurate one since stroke is rarely an ‘accident’. The underlying conditions of a stroke (called cerebrovascular disease) are usually present for years before a stroke occurs, although the symptoms of a stroke may occur suddenly.

There are sometimes quite specific warning signs of an impending stroke. By recognising the warning signs and taking action, you may be able to avert a stroke or reduce its severity. Almost 50 per cent of people who go on to have a stroke experience warning signs or a small episode called a transient ischaemic attack. It is important to be able to recognise the warning signs in order to get medical help as quickly as possible.

Transient ischaemic attacks

Transient ischaemic attacks (TIAs) are caused by a temporary cut in blood supply to the brain, due to the partial blockage of an artery by a blood clot or debris. TIAs have the same symptoms as a stroke, but they are temporary and do not usually cause long term brain damage. A TIA, or mini-stroke, is a warning of an impending stroke. A person who has had a TIA is at greater risk of having a stroke or heart attack. Early identification of symptoms and a diagnosis from your doctor greatly reduces the chances of a major stroke. A TIA is:

* Transient - symptoms usually last for less than 24 hours.

* Ischaemic - failure of blood flow to part of the brain or eye.

* Attack - sudden onset of symptoms, which vary from person to person, depending on which part of the brain or eye is starved of blood.

Symptoms of a stroke

Symptoms of a TIA are very similar to those of a stroke. They can include:

* A numb or weak feeling in the face, arm or leg.
* Trouble speaking or understanding.
* Unexplained dizziness.
* Blurred or poor vision in one or both eyes.
* Loss of balance or an unexplained fall.
* Difficulty swallowing.
* Headache (usually severe or of abrupt onset) or unexplained change in the pattern of headaches.
Confusion.

Unconsciousness.

If you suddenly experience any of these symptoms, get straight to a hospital. Remember, stroke is a life threatening emergency.

Symptoms occur in a variety of ways

The warning signs or symptoms of stroke may occur alone or in combination. They may last a few seconds or up to 24 hours, and then disappear. These signs are mini-strokes and should not be ignored. They indicate a hidden problem with blood flow, which could trigger a stroke. The severity of the symptoms depends on the area of the brain affected, and the cause.

Where to get help

* Your doctor
* Emergency department of your nearest hospital.

Things to remember

* The symptoms of stroke can occur suddenly.
* Transient ischaemic attacks (TIAs) are an important warning sign that a stroke may occur in the future.
* Early identification of symptoms and a diagnosis from your doctor greatly reduces the chances of a major stroke.

Related fact sheets:

Stroke - the after effects.
Stroke - the risk factors.
Stroke and high blood pressure.
Stroke and migraine.
Stroke can occur in children.
Stroke is a brain attack.Stroke prevention.
Transient ischaemic attack.